chg: pass sensitive command line flags to server

We are going to make chgserver load repo config, remember what it is, and
load repo config again to detect config change. This is the first step that
passes config, repo, cwd options to server. Traceback is passed as well to
cover errors before hitting chgserver.runcommand.

contrib/chg/chg.c

@@ -32,8 +32,80 b' struct cmdserveropts {'
 	char sockname[UNIX_PATH_MAX];
 	char lockfile[UNIX_PATH_MAX];
 	char pidfile[UNIX_PATH_MAX];
+	size_t argsize;
+	const char **args;
 };
 
+static void initcmdserveropts(struct cmdserveropts *opts) {
+	memset(opts, 0, sizeof(struct cmdserveropts));
+}
+
+static void freecmdserveropts(struct cmdserveropts *opts) {
+	free(opts->args);
+	opts->args = NULL;
+	opts->argsize = 0;
+}
+
+/*
+ * Test if an argument is a sensitive flag that should be passed to the server.
+ * Return 0 if not, otherwise the number of arguments starting from the current
+ * one that should be passed to the server.
+ */
+static size_t testsensitiveflag(const char *arg)
+{
+	static const struct {
+		const char *name;
+		size_t narg;
+	} flags[] = {
+		{"--config", 1},
+		{"--cwd", 1},
+		{"--repo", 1},
+		{"--repository", 1},
+		{"--traceback", 0},
+		{"-R", 1},
+	};
+	size_t i;
+	for (i = 0; i < sizeof(flags) / sizeof(flags[0]); ++i) {
+		size_t len = strlen(flags[i].name);
+		size_t narg = flags[i].narg;
+		if (memcmp(arg, flags[i].name, len) == 0) {
+			if (arg[len] == '\0') {  /* --flag (value) */
+				return narg + 1;
+			} else if (arg[len] == '=' && narg > 0) {  /* --flag=value */
+				return 1;
+			} else if (flags[i].name[1] != '-') {  /* short flag */
+				return 1;
+			}
+		}
+	}
+	return 0;
+}
+
+/*
+ * Parse argv[] and put sensitive flags to opts->args
+ */
+static void setcmdserverargs(struct cmdserveropts *opts,
+			     int argc, const char *argv[])
+{
+	size_t i, step;
+	opts->argsize = 0;
+	for (i = 0, step = 1; i < (size_t)argc; i += step, step = 1) {
+		if (!argv[i])
+			continue;  /* pass clang-analyse */
+		if (strcmp(argv[i], "--") == 0)
+			break;
+		size_t n = testsensitiveflag(argv[i]);
+		if (n == 0 || i + n > (size_t)argc)
+			continue;
+		opts->args = reallocx(opts->args,
+				      (n + opts->argsize) * sizeof(char *));
+		memcpy(opts->args + opts->argsize, argv + i,
+		       sizeof(char *) * n);
+		opts->argsize += n;
+		step = n;
+	}
+}
+
 static void preparesockdir(const char *sockdir)
 {
 	int r;
@@ -111,7 +183,7 b' static void execcmdserver(const struct c'
 	if (!hgcmd || hgcmd[0] == '\0')
 		hgcmd = "hg";
 
-	const char *argv[] = {
+	const char *baseargv[] = {
 		hgcmd,
 		"serve",
 		"--cwd", "/",
@@ -122,10 +194,18 b' static void execcmdserver(const struct c'
 		"--config", "extensions.chgserver=",
 		/* wrap root ui so that it can be disabled/enabled by config */
 		"--config", "progress.assume-tty=1",
-		NULL,
 	};
+	size_t baseargvsize = sizeof(baseargv) / sizeof(baseargv[0]);
+	size_t argsize = baseargvsize + opts->argsize + 1;
+
+	const char **argv = mallocx(sizeof(char *) * argsize);
+	memcpy(argv, baseargv, sizeof(baseargv));
+	memcpy(argv + baseargvsize, opts->args, sizeof(char *) * opts->argsize);
+	argv[argsize - 1] = NULL;
+
 	if (execvp(hgcmd, (char **)argv) < 0)
 		abortmsg("failed to exec cmdserver (errno = %d)", errno);
+	free(argv);
 }
 
 /*
@@ -352,7 +432,9 b' int main(int argc, const char *argv[], c'
 		enabledebugmsg();
 
 	struct cmdserveropts opts;
+	initcmdserveropts(&opts);
 	setcmdserveropts(&opts);
+	setcmdserverargs(&opts, argc, argv);
 
 	if (argc == 2) {
 		int sig = 0;
@@ -379,5 +461,6 b' int main(int argc, const char *argv[], c'
 	setuppager(hgc, argv + 1, argc - 1);
 	int exitcode = hgc_runcommand(hgc, argv + 1, argc - 1);
 	hgc_close(hgc);
+	freecmdserveropts(&opts);
 	return exitcode;
 }